Photoelectron impact ionization (PEI) of noble gases has been investigated in a time of flight mass spectrometer (TOF-MS). Multicharged ions of He, Ne, Ar, Kr and Xe were produced when the gases were injected into the ionization region and a focused laser beam struck the extractor grid surfaces in the TOF-MS. A delayable pulsed accelerating electric field was used, for the first time, to test the effect of the laser induced photoelectrons on the ionization. A special photoelectron gun was designed to control the energy of the photoelectron beam. This modification made it possible to separate the PEI from multiphoton ionization (MPI). The observations showed that the multiple charged ions could be only formed by the PEI in our experiments, possibly formed step by step. With the new design of the electron gun, the TOF-MS can be operated in either MPI mode or PEI mode.